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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6877b35cc0680666fcfb28c0874c6f1f6f47e5c263a2f91a1abc7f28950341a' 
  AND token = 'C5o8lWux1np6jqbiUNJx9r+qLSuCMxhDm453iMNHRmU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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