SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29ec0355d264f8ff1842ff984226cb1cdf4573cec58d4ade28905ec245e02b21' 
  AND token = '7nt3mkSkyJ1Pr17OwS7zmrjuPDBFloQm5t3spfzLDvE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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