SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c15a2feaad39f57507b7544bd6f4428f0e3f07c888da04904c5dafa591d6b27a' 
  AND token = 'uOkRPNnWQM1kgxluDDsQCpzffSSns5iTcK4wEAhYsZs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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