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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '627037aa6fcd2e9f46ecb6ec1db4a878ebfda39f228cf5af97e354adb0c5b8ca' 
  AND token = '+JEOvjeg7waxdc9ZqkC/bVITNbR8+DSTOfeMNrNiLAE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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