SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75e70fddbf827328860b741475a9a5173028f9c883866bb545d5d6bb3a77b2a8' 
  AND token = '1xUNAXLiCrzGCPzhnTaqJrN6+Ar1L/HjDb8LYPZI0f0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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