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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b92041f99f51f6c9052323fdd94c3540b4c05cb23efbd42c7e8356bfd2e7e73e' 
  AND token = 'CkmUB/hTaL2iWJ6D3pkvbrpzAro+LqlTVkVNkMwX9H0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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