SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '375bd6a6a8d747bc9142f35546c8a059cf4da0bf4decba4796ced964f0e01e45' 
  AND token = 'gaTJQjQgNP3gaLMF/+RGP0ypmkOE3QiSd8wP3azZbUI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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