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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50957e3180f0eb9ff8381f63d05d5afd28455dd9e5f2a701f9b2e89e7cb3f29b' 
  AND token = 'a3+jMmETBQPKH8P2B5eSQyHZa2f/ud5UEFNqJi4SLKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}