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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f91ee37efd2c3cdc3aa976318e854c834daaf11f06c7c5b3bfa43769778b1f75' 
  AND token = 'L5cYRgkQu5ekk+iiIhhHlyzjL6Femkc0WK+nq4HiIwo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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