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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55f35ba0d1c0fcb320c4889f640f17b2bf1c990c28b29583a70b415ee3612b85' 
  AND token = '3mbYF3/SAMACj2TIHvI8bCmrvVEv2JSlrf4mxGXYQyg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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