SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '579376391070c2a1146b3c30347dedde84687a54ed08caa447808977346841f0' 
  AND token = '5wziX8v3SV98koTgjQVMo0BDh/vO3DrVWtuN+37oLTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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