SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75c78579a790fa183f46daf311db39ba02dec2af627cdabc55aeee118738b64e' 
  AND token = 'iU8vvzXDTqXGVkGhirKd1hNAtRh8/qjwqES6U7X/QBQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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