SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0b2871193e0dbde349624326657535d53796b45fea00925fcc2e3992d004ec3' 
  AND token = 'u6G82IvymrKJj1tazi2eJVsDBIBjMLODm1eqfsVSfCI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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