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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3e0c04817cc3d85313315f44b3c5e7421bb8f038a944d3a23e014009b4f28bd' 
  AND token = '3iwg4+RnNnqM2wQ/Y1bucAtmi6ZmY0I0SN/C8Z+GQ/w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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