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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '243e5043e1bf65b2f298c3d654e6d7ff7b2311012120d12afd2f051a9a625b3e' 
  AND token = '1CdmSb2Y9gr4K1oNh9ePpvhqdcPZ2QKfU0A5Q/Aiz44=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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