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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a335afc21aae2a61e2c8b7c5ade4f9b7a4a267c2071329ed4eed34a0fc2f508a' 
  AND token = 'h+oGlY1OPUz2wFUoDh5dyRY7CQCm8/qQxvm1FvxFE08=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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