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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4b6ffe1d6123af1214692676104d71e5a83e0e2d2be70e1b8c72d914c0f8ba4' 
  AND token = 'm0JZ+GWb6kt6NqrRmkmhYS0oRrfGbDv2HOcrF26ahD0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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