SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cae3a29bec6172f7641094ac573279a72c273758f3392eeac66045c7190758bb' 
  AND token = 'CPLEvhv5Uc/Gw5UBe1B4ygQ7IyMSc/BQB7epwWW2ixM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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