SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '278a7afbdad70e9ffbb2b397f6fc85b5241a973e95ca2d9314d171063bc52875' 
  AND token = '7+Ev4ZLfxu0Mm98vgybf8+nw2PDa+4plZCAC+SGZFow=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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