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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3cde28e32cfe6bb9dd8d2cd3e275a17612b5fad9edd1e91a1017f4eb2242ee2' 
  AND token = 'VqiZ/J8yTCbh2jpZVDX++pBnTmbLwrEkuTaGVXqgal4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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