SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf3457bc05d57579dd7cbea13c304a531166f2fa651be1fe653e12f79975a778' 
  AND token = 'MnxFGZx3VVUuy4voCapRgSeq5WrtMhRxevCttJerI3w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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