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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db39a2a9ffdcc60477a0945e44da0d87df018b54cbadb4dc80d3116aaa86f738' 
  AND token = 'QkCUHz4YilGctGWOj2DskvstnnEb6mkFZbBb+8l9xcw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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