SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55bc093d9eff001f4614d59956c3db90526b64c07034b892541aff4a30e47381' 
  AND token = '+xmQEo6CgKPrb4YJLCTLRTsw+OPVhgcDjDmKkjv9JC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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