SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31aa0e8f09cea4ee87305c9d1591e158763de763e8fb95e9e146e962c4dad1ac' 
  AND token = 'u/jQxXiqYSGoxZ9jCbXw6AjhPCv5+Ksn8H9B7ArglHA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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