SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b5816e32c134dbb2bf3e2aad103b7d9a1934752f5b4d0189d5bcfe714997c0' 
  AND token = 'SQTPmTjhtHfwFQ+/kNFuJIhHiosG36rnoEIa9X6KzWs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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