SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c8cf335af294b598ffe97ef1f85e414fbf52c25c5bffbe81dd7a6a7e8120ede' 
  AND token = 'fdJ6HObd62X4vBebaVmVrSkUHejtVbruEK/dEAGDOrg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}