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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3f7d9f2d3f726c0a0039b5414ed9130324a642b3dfd2bc56caee990fae6c6b6' 
  AND token = 'p/7DzpcqFgHyZJMT9msMkUvRXTkn0i+s8qBBkm0r7Bc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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