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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f5796974ebbc960a0a2f9a2251d82794411b8e9760d1e89b4274af1f44517ad6' 
  AND token = '8UD1zuijtSE6CtTj779X5txEpz5ze6KwiOGuclhsPtU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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