SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3139a4ef632d4b3d50816a3524d926898e3a1e31b5878d39c13f6763c46ce2de' 
  AND token = 'KmwsRRO+fz/hZzZ24BtDSxC1wnqcgpvmcsFl6mQwTsY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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