SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df6950c33137b37746b8e7a67a51d8a3e44c7070f61e755da9b45a989c88a78e' 
  AND token = 'u+Wk7Y1ApiyOgBh+fmpYzTVHCcc/vDmM+alS2G9weJs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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