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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2c7e8a47bc6941a83b87077fb55a37e526dbb9f7ed60e6d82331c17458a1aaa5' 
  AND token = '6xKlHMpgPKZ4BKXCe3Gnbu7N63SmOq+JNgG3y2NCa6E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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