SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '678774d128d264e0f45aa39fc1491d2e8cadd513d2d19ad960f4fe21fa56885f' 
  AND token = 'o8ajfcOVROlUlB+vOAWVGZ4mW8DXcXpY9pLZgDyp2wY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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