SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75d60310e28f696e6705e50be87a7c1606e225c1721ed232bddbe57bb57ab428' 
  AND token = 'HSdkAtu9UUMaCRIa+xsGnh+6Yjo/BFw2UB82cOFk4vQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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