SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5920cb901af7acea1432159d390aee3b6934404367bf299d010818a69038c408' 
  AND token = 'iI2x1hwoWLelXVl/VFw0PTceZIwvTBEoAgwCIWPJmrs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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