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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe714f3c984d30b0ae513800522184d8ff279409657458f1e79bd18eff2db312' 
  AND token = '15HRrn5VGygJQLis7ZIPmjcMN8aEniWuVPpY8jrO9rM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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