SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '759311c3d025393f42bb5729da54c257b5362e99dfdfae57e6711847f9279a87' 
  AND token = 'HNYA25ffbIfxOfojlpmDKiTVacPjnHZkacmAfVkwJ0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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