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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a71b8afd20a770ae7587cbd987692e340890884c9280f8d741ed2fa7d7d64918' 
  AND token = 'UF753wvbLrsiMm6tsbrU7WKBUs36L0FnUnprjbajq4Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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