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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4a3320c46f6d4595c035d793aa7f6a2f59f6dfdc1bf8a8ac3e543c4efa92f99' 
  AND token = 'UDXxkA7+0Kl5RFkwv3ICU+aSgeCHWKk7OIAjwM4e1YQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}