SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b592426f36d9436437f2a186c76a5795b6b13440652682cf4c1a5dc29cfaf662' 
  AND token = 'tvNmamwICdQKHJB510L/Rpu6ByMO4EVhJm3Ca4ujbkY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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