SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b6ebceb1ec9739ccc4db9ed83894908bd5bb3caf0ffd9d2880a7c1c5d78b308' 
  AND token = 'SG/7vtr5UB9F5N+dD2giU+A6hrGniJ4bVvyW/+rn2Qo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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