SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd90e0f51f2fb6e9899215fd9a4c941d6331d74866206521096fd3049382f5a6c' 
  AND token = 'U4U+GJoYRWPhikvjeq+aDjpQJRJDkKOIIVBc90BJEGk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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